Machine and process for corner bending corrugated sheet



Jan. 10, 1961 R. H. THOMS 2,967,560

MACHINE AND PROCESS FOR CORNER BENDING CORRUGATED SHEET Filed June 11,1956 4 Sheets-Sheet 1 IN V EN TOR. Papa/w 7/7 0440" Jan. 10, R. H. THOMSMACHINE AND PROCESS FOR CORNER BENDING CORRUGATED SHEET Filed June 11,1956 4 Sheets-Sheet 3 20d Q 20c V05 22 INVENTOR.

ATTO/P/VE Jan. 10, 1961 R. H. THOMS 2,967,560

MACHINE AND PROCESS FOR CORNER BENDING CORRUGATED SHEET Filed June 11,1956 4 Sheets-Sheet 4 MACHINE AND PROCESS FOR CORNER BENDING CORRUGATEDSHEET Rudolph H. Thorns, Cleveland, Ohio, assignor to Republic SteelCorporation, Cleveland, Ohio, a corporation of New Jersey Filed June 11,1956, Ser- No. 590,647

11 Claims. (Cl. 153-21) The present invention relates to cold-formedsheet metal articles and their forming processes and machines. Moreparticularly, the invention relates to articles which embody formedcorners, and to processes and machines for cold-forming of such corners,transverse to corrugations which are provided in the sheet metal fromwhich the article is formed and which contribute to enhanced strengthand rigidity of the finished article.

In the interests of economy, lightness, and ease of fabrication, manyarticles are formed from relatively light weight sheet metal and employsome form of corrugation or ribs by which to increase the strength andrigidity of the article equivalent to that of one formed fromnoncorrugated sheet or other metal of much heavier weight. Often thecorrugations or stiffening ribs are stamped out of the sheet metal afterthe blanking step and most or all of the forming steps are completed,but there are many instances where economy and ease of fabrication makeit highly desirable suitably to corrugate a base sheet metal prior toany forthcoming step. Much difiiculty is experienced in those instanceswhere it is desired to provide a cold-formed corner bend in the corrugated metal transverse to its corrugations, and heretofore this hasbeen accomplished largely at a sacrifice of corner strength and rigidityby more or less deformation of each corrugation in the region of thebend. To avoid erratic and more-or-less uncontrolled deformations ofthis nature, it has peen proposed that the bending step be accompaniedby deliberate and positionally controlled deformations in the form ofpositioned creases or indentations symmetrically extending throughoutthe corner bend region. Nevertheless a corner bend transverse to thecorrugations has heretofore often resulted in a structure so weakened asto necessitate the use of one or more strengthening straps bridging thecorner and afiixed to points spaced some distance to each side thereof.

Where articles formed of sheet metal are used in food handling andprocessing, it is highly desirable that the article have smooth surfacesthroughout not only to facilitate sanitary cleansing but in fact toassure it. Additionally, and perhaps equally important, it is desirablethat the article be completely devoid of any sharp closed-in corners, orcracks or crevices in which food may collect and develop bacteria. Thusin a food handling article involving corner bends transverse tocorrugations it is highly undesirable to have deformation in the natureof wrinkles or indentations at corner bends of the corrugations or touse corner bracing straps or the like as above described.

It is an object of the present invention to provide a new and improvedmethod and process for forming corner bends in corrugated sheet metal,transverse to the corrugations thereof, while enabling the preservationof substantially uniform corrugation cross-sectional configuration andsmooth corrugation wall surfaces throughout the bend.

It is a further object of the invention to provide a novel method andmachine for forming corner bends transverse to the corrugations ofcorrugated sheet metal. while minimizing corrugation distortion in thebend,

thereby enabling the attainment of substantially optimum corner strengthand rigidity obviating the need of corner braces and characterized bysmooth and crevice:

free corner surfaces.

It is an additional object of the invention to provide a new andimproved method and machine particularly suited for forming corner bendstransverse to the corrugations of corrugated sheet metal of those typeswhich are difiicult to work as typified by stainless steel and titanium,including titanium alloys.

It is another object of the invention to provide a novel articlecold-formed of corrugated sheet metal, and particularly one cold-formedof corrugated stainless steel sheet or corrugated titanium sheet, havingstiffening and rigidizing skirts or flanges yet one exhibiting smoothsurfaces throughout free of sharp corners, cracks and crevices andtherefore one particularly suited for use in handling and processingfood stuffs.

It is a further object of the invention to provide a new and improvedmachine for corner bending corrugated sheet metal of thehigh-melting-point types, typified by stainless steel, transverse to itscorrugations while faithfully preserving uniform corrugationcross-sectional configuration to enable the fabrication of articleshaving corner bends possessing to a high degree the desirablecharacteristics attributable to this type of construction.

Other objects and advantages of the invention will appear as thedetailed description proceeds in the light of the drawings forming apart of this application and in which:

Fig. 1 illustrates in elevational side view, and Fig. 2 in elevationalend view, a platform embodying the present invention and particularlysuitable for use in handling and processing food stuffs;

Fig. 3 illustrates in cross-section, and partly diagram- 'matically, theconstruction of a machine embodying the invention for cold-formingcorner bends in corrugated sheet metal, and Figs. 4 through 7 arecross-sectional views illustrating the operation of the machine atvarious points in its operating cycle, Figs. 4 through 6 being enlargedviews of the bending dies shown in Fig. 3 and Fig. 7 an enlarged sectionon line 7-7 of Fig. 6;

Figs. 8 through 10 illustrate the construction of a corner bendingmachine embodying the present invention in modified form.

Referring now more particularly to Figs. 1 and 2, there is illustrated aplatform embodying the invention and particularly suitable for holdingmeat during storage and while cooking it. The platform is of double-deckconstruction and includes two similar platform sections 10 and 10 eachhaving a platform portion 11, 11' and depending skirt or side portions12, 12' joined to the platform portion by a right angle corner bendportion 13, 13'. The side portions 12, 12 terminate at their bottom edgein inturned feet portions 14, 14 as shown, and differ from each otheronly in length as between the lower and upper platform. The sideportions 12, 12' provide enhanced stiffness and rigidity to the platformportion 11, 11, the side portions 12 having sufficient length for theinsertion under the platform of a suitable transportation dolly or theforks of a fork-lift truck while the side portions 12' of the upperplatform provide additional a melting point in excess of 2,000 P.) whichis usually considered as difiicult to work but possesses such desirableproperties as highstrength and high resistanceto oxidation andcorrosion. Typical of such metals are stainless'steel sheet or titaniumsheet. Each platform is shown as fabricated of sheet metal havingregularly spaced corrugations of isosceles trapezoidal cross-sectionenabling a high degree of stiffness and rigidity with minimum weight ofsheet metal, and the two platforms are integrally united by uprightspacer members 15 which are arc welded around the entire juncture of theupright and platform and the welded region is thereafter ground to asmooth welded surface free of cracks and crevices in which food maycollect and develop bacteria. The uprights 15 have their center portionsrecessed by a conventional drawing or stamping process for increasedstrength and rigidity of these members. The corner bends 13 and 13 ofthe platforms have a radius of curvature approximately twice that of thedepth of corrugation, and are so formed in a manner presently to bedescribed as to have uniform cross-sectional configuration and smoothside walls throughout the length of the corner bend. The platformaccordingly possesses smooth surfaces throughout without hidden sharpcorners, cracks or crevices, a construction which greatly facilitatesand readily insures proper cleansing for reasons of sanitation.

By Way of example, an article embodying the present invention has beenformed of 13 gauge (0.093 inch) stainless steel sheet havingcorrugations of /8 inch depth with an isosceles trapezoidalcross-section having walls forming an angle of 60 with the surface ofthe article. A radius of curvature of 1 inches, related to the outersurface of the corner bend, is readily attainable for a material of thetype and having corrugations of the shape and size last recited whileyet retaining uniform corrugation cross-sectional configuration andsmooth corrugation wall surfaces throughout the bend.

The present invention as embodied in one. form of machine for formingcorner bends in corrugated sheet metal as above described is illustratedin elevational cross-sectional view, partly schematic, in Fig. 3 andcertain additional details of construction are illustrated in thefragmentary cross-sectional view of Figs. 4 through 7 which illustratessuccessive stages in each cycle of operation of the machine. Referringparticularly to Figs. 3 and 7, the machine incindes a stationary diemember 20 suitably secured to the bed (not shown) of a power press ofconventional construction. The die member 20 has a V-shaped concavegroove 21 defining the desired angle and radius of curvature of thecorner bend, here shown by way of illustration as defining a rightangled corner bend of 1 /2 inch radius. As shown more clearly in Fig. 7,the die member 20 is conveniently constructed in a plurality of sectionsZOa-Ztld each having an associated insert 22 with an upper surface 25 ofconvex curvilinear configuration. The width of each die member sectionand its associated insert 22 corresponds to the corrugation spacing.These sections of the inserts 22 are relatively positioned by the use oflocating pins (not shown), and are suitably bolted or clamped togetheras a unitary structure by means not shown. As many die member sectionsand associated inserts are used as the width ofthe sheet metal to bebent requires, thus providing a rather flexible form of die memberconstruction in which die member sections and associated inserts may beadded or subtracted as required for the forming of articles of differ.-ent widths without necessitating the construction of an individual diemember for each such width.

The upper surfaces 23 of the die member sections20a- 20d are planar andprovide initial support for the generally planar corrugated sheet metal24 in which it is desired to form a corner bend. The upper surfaces 25of the inserts 22 support an individual temporary deformable metal diemember 26 initially of generally linear configuration. One die member 26is positioned, either before orafter positioning of the sheet metal 24,within each corrugation of the sheet metal and has a cross-sectionalconfiguration related to that of the. corrugation. For. ex-

' seemed ample, the temporary die members 26 may convenientlyhavecircular cross-section when used with corrugations of isoscelestrapezoidal cross-sectional configuration, the diameter of such diemember being selected such that it engages the opposing side wallsurfaces of the corrugation at the initiation of the corner bendingoperation and preferably also engages the apex surface of thecorrugation at the outset of the bending operation or immediately afterthe bending step starts. For corrugations havingthe cross-sectionalconfiguration and dimensions hereinbefore mentioned, the temporary diemembers 26 may have a diameter of /2 inch and are formed of untemperedbut suitably stiff metal such as hot-rolled low-carbon-content steel rodwith unpolished surfaces. For use with stainless steel or titanium, thetemporary die members 26 are used without grease or other lubrication.These emporary die members 26 may have short prccut lengths or may eachbe comprised by the end portion of a much longer length of metal rod.

A front gauge 27 is suitably affixed to the die member 20 and has anupper end 28 extending within each corrugation for use as a positioningstop for locating the forward end of each temporary die member 26. Aback gauge 29 is also affixed to the die member 20 in any suitablemanner to provide a positioning stop for engagement by an edge portionof the sheet metal 24 positionally to locate the sheet metal withrelation to the die member 20 and thereby establish the position of thecorner bends in the sheet metal.

The corner bending machine also includes a punch die member 32 which, asshown in Fig. 7, may be constructed in demountable sections 32a-32erelatively positioned in conventional manner. by locating pins, notshown, and suitably bolted or clamped together as a unitary structure.The die member 32 is suitably secured to the slide 33 of the powerpress, the slide 33 being supported by ways (not shown) forreciprocatory motion in conventional manner. The lower end of each punchdie member section 32a-32e has a convex contour conforming to the formedsurface 21 of the die 20, and each is provided with a centrallypositioned groove 34 of the same cross-sectional configuration as thecorrugations of the sheet metal to receive the corrugations and preservetheir exterior configuration during the corner bending process.

As shown schematically in Fig. 3, the slide 33 of the power press isdriven through each cycle of reciprocatory motion by any suitable means.For simplicity of illustration, mechanical means are shown in Fig. 3,for driving the slide, as by a crank arm 31 which connects the slide 33to a conventional crank shaft 35 mechanically connected through a cyclecontrollable clutch 36, ring and pinion gears 37, pulleys 38 and 39, anda belt 40 to a source ofjmotivating power 41 such as an electric motor.

he clutch 36 includes a yoke 42 mechanically connected through suitablelinkage 43 to a manually operable hand lever or foot pedal 44 by whicheach punch cycle is initiated in conventional manner.

The sheet metal 24 is cut and blanked (and pierced if piercing isdesired) while in sheet form, and is thereafter corrugated as by the useof conventional corrugating rolls. Certain initial bending or formingsteps may then take place, such as bending the feet 14 of the platform.The sheet metal and temporary die members 26 are then placed in thepower press and positioned by use of the respective gauges 27 and 29,and the machine is initiated through a punch cycle of operation byactuation of the hand lever or foot pedal 44. Figs. 4' through 7illustrate successive stages of the punch cycle of operation startingfrom. the initiation of the cycle as shown iniFi'g. 3 and continuingthrough one-third of the punch down-stroke illustrated in Fig. 4,two-thirds of the punch down-stroke illustrated in Fig. 5, and thecompletion of the down-stroke as. illustrated in end cross-sectionalview in. Fig. 6and side cross-sectional view in Fig. 7.

games It will be noted from these several illustrations that thetemporary die members 26 are supported by the die member 20 at regionsremote from the region of corner bend of the sheet metal 24, that thetemporary die members 26 are conformably bent concurrently with thecorner bending of the sheet metal 24 by bending stresses imparted to thetemporary die members 26 through the sheet metal 24, and that throughoutthe corner bending step the temporary die members 26 support the sideWalls of each corrugation and preferably also bear against the insideapex surface of the corrugation to maintain the corrugation wall spacingthroughout the corner bending process.

The precise manner in which the temporary die members 26 maintainsubstantially uniform corrugation crosssectional configuration andsmooth corrugation wall surfaces throughout the corner bending processis not fully understood, but it is believed that these desirable resultsare produced by frictional forces set up by engagement of the temporarydie members 26 with the inside wall surfaces of the corrugations ratherthan by the heaviness or stiffness of the material of the temporary diemembers 26. These frictional forces all along the length of eachtemporary die member 26 are believed to increase as the bend progressesand appear to be accompanied to more or less extent by a draggingeffect, thus holding quite firmly the inside wall surfaces of thecorrugation and doubtless causing some actual wall compression. It hasbeen found in practice that the temporary die members 26 may have asomewhat loose fit with the corrugations at the initiation of the cornerbending operation, a perfect fit appearing not to be required, and thatthey snug up with the corrugations as soon as the actual bendingoperation begins. Since the crest of each corrugation is received withina groove 34 of the punch die member 32, the grooves 34 appear to guidethe compressive flow of the sheet metal in the crest during the bendingstep. At the moment of full closure of the die members 20 and 32, thetop surface of each insert 22 engages an associated die member 26 toforce the latter fully into its corrugation and thereby force the sidewalls and apex of the corrugation into conforming engagement with anassociated groove 34 of the die members 32 as a final corrugationforming step.

Upon completion of the down stroke of the punch die 32 as illustrated inFigs. 6 and 7, the die 32 is automatically raised again to complete itsreciprocatory cycle and fore the fatigue of the metal of the temporarydie renders the latter unsuitable for further use, or the bent end ofeach temporary die may be cut off and discarded as scrap where thetemporary die is composed of only the end portion of a long length oftemporary die material.

Since the cross-sectional configuration remains uniform and withoutdistortion and with smooth corrugation walls throughout the corner bend,an article formed with corner bends in accordance with the presentinvention is characterized by corner bends of much greater strength andappreciably greater rigidity than heretofore exhibited by prior cornerbends of deformed cross-section even though strengthened by bridgingbracing corner straps as heretofore described.

A form of corner bending machine embodying the present invention inmodified form suitable for hand operation is illustrated in Figs. 8, 9,and 10. This form of machine is in the nature of a sheet metal brakehaving a bed 50, supported on a stand 51, to receive and position thecorrugated sheet metal 24 and temporary deformable die members 26 forthe corner bending operation. A

hinges 53 to the bed 50 or stand 51 as in conventional 6 metal brakeconstructions and is movable by manual force exerted on a handle 54 orlike actuator affixed to the plate 52. A hold-down member 55 issupported in convcntional manner by guides or ways (not shown) formovement toward and away from clamping hold-down engagement with thesheet metal 24 on the bed 50, and has a lower corner 56 rounded todefine the radius of curvature of the corner bend which it is desired toform in the sheet metal. The hold-down member 55 is provided withgrooves 57 to receive the corrugations of the sheet metal 24 initiallyand at the completion of the bending operation, as illustrated by thefragmentary cross-sectional view of Fig. 9. As also illustrated in Figs.9 and 10, a plurality of metal strips 58 are suitably secured to the bed50 and bending plate 52 in registry with the corrugations of the sheetmetal and have convex surfaces engaging the temporary die members 26 toserve the same purpose as the insert members 22 of the machine earlierdescribed.

The operation of a machine embodying the present form of the inventionis believed evident from the foregoing description considered inconnection with the drawing. Manual actuation of the handle 54 iseffective to move the bending plate 52 about its hinge point 53 to bendthe corrugated sheet metal 23 and temporary die members 26 by exertingbending stress on the temporary die members 26 at points removed fromthe region of bend of the sheet metal. The curved corner 56 of thehold-down member 55 engages the sheet metal 24 at the region of the bendto effect concurrent bending of the sheet metal 24 and temporary diemembers 26 to the desired radius of curvature. The grooves 57 of theholddown member 55 and the temporary diemembers 26 cooperate during thebending process in much the same manner and to attain the same result asdescribed in connection with the machine of Figs. 3-7.

From the foregoing description of the invention, it will be apparentthat the invention enables the coldforming of corner bends transverse tothe corrugations of corrugated sheet metal (e.g. of iron, steel and thelike, and particularly special metals as described above) whilepreserving maximum stiffness and rigidity of the corner thus formed toobviate the need of any corner bracing. Articles so cold-formed inaccordance with the invention 'accordingly possess high strength andstiffness and exhibit scribed for purposes of illustration, it iscontemplated that numerous changes may be made without departing fromthe spirit of the invention.

What is claimed is:

1. The method of forming corner bends in, and transverse to thecorrugations of, corrugated sheet metal While maintaining substantiallyuniform corrugation crosssectional configuration and smooth corrugationwall surfaces throughout the bend comprising: positioning the corrugatedsheet metal between spaced-apart corner bending dies With the sheetsupported on one of said dies at places spaced apart in the direction ofsaid corrugations, including in cooperative relation with eachcorrugation a temporary deformable metal die member dimensioned tomaintain corrugation wall spacing and positioned to receive bendingstresses through said sheet metal and having a length correspondingsubstantially to the ultimate length of engagement of said bending dieswith said sheet metal, and closing said dies to exert a bending force onsaid sheet metal at the region of said bend and counterforces on saidtemporary die members at regions removed from said region of bend toform said bend while concurrently conformably bending each saidternporary die member by bending stresses imparted thereto through saidsheet metal.

2. A corrugated stainless steel sheet or plate metal corner bendingmachine comprising, a pair of corner bending dies supported for relativemovement between open position receiving said sheet or' plate metaltherebetween and closed position at which a desired corner bend isformed and including a convex die member having grooves ofcross-sectional configuration corresponding to that of said corrugationsto receive said corrugations as the bend progresses and including amating concave die member, the corrugations of said sheet metal havingisosceles trapezoidal cross-section, said sheet or plate metal beingsupported by said concave die member with the corrugations thereofspanning said concave die member in the direction of their length, atemporary deformable metal die member of circular cross-sectionindividual to and positionable within and extending substantiallythroughout the ultimate die-engaged length of each corrugation includedin a corner bend, the diameter of said deformable metal die membersbeing selected with relation to the corrugation wall spacing to maintainsaid wall. spacing during corner bending thereof, and means foreffecting forced movement of said corner bending dies to said closedposition concurrently to bend said sheet metal and each said temporarydie member.

3 The method of forming corner bends in, and transverse to thecorrugations of, corrugated sheet or plate metal while maintainingsubstantially uniform corrugation cross-sectional configuration andsmooth corrugation wall surfaces throughout the bend comprising:positioning the corrugated sheet or plate metal between opposing andrelatively movable corner bending members with the corrugationspositioned perpendicular to the region over which the corner bend isdesired, one of the said members having corrugation-receiving grooves ofcross-section substantially corresponding to that of the corrugationsand also extending substantially perpendicular to said region of bend,positioning within each corrugation in engagement with at least opposingside-wall areas thereof an elongated initially linear but deformablemetal member extending beyond said region of bend on each side thereof,and applying bending forces to said corner bending members to providerelative movement between said corner bending members to form said bendby said forces being exerted on said sheet or plate metal and each saiddeformable member at said region of said bend.

4. The method of forming corner bends in, and transverse to thecorrugations of, corrugated sheet or plate metal while maintainingsubstantially uniform corrugation cross-sectional configuration andsmooth corrugation wall surfaces throughout the bend comprising:positioning the corrugated sheet or plate metal between spacedapartmating convex and concave corner bending die members with thecorrugations spanning said concave die member, one of said die membershaving corrugation receiving grooves of cross-section substantiallycorresponding to that of the corrugations and extending substantiallyperpendicular to the region of said one die member over which the cornerbend in said sheet or plate is to be formed, including in cooperativerelation with each corrugation on the side of said sheet or plateopposite said groove die member and extending over the span of saidconcave die member a temporary deformable metal die member dimensionedto maintain corrugation wall spacing, each said deformable die memberreceiving bending forces exerted thereon by the non-grooved one of saiddie members and said sheet or plate receiving bending forces exertedthereon by said grooved die member, and closing said die members to formsaid bend while concurrently conformably bending each said temporary diemember by bending stresses imparted thereto through said sheet or platemetal.

5. The method of forming corner bends in, and transverse to thecorrugations of, corrugated sheet or plate metal while maintainingsubstantially uniform corrugation crosssectional configuration andsmooth corrugation wall surfaces throughout the bend comprising:positioning the corrugated sheet or plate metal between spaced-apartcorner bending dies including a convex die member grooved to receivesaid corrugations as the bend progresses and including a mating concavedie member, thecorrugations of said sheet or plate spanning said concavedie member, including Within each corrugation a temporary deformablemetal die member spanning said concave die member and dimensioned tomaintain corrugation wall spacing and to receive bending stressesthrough said sheet or plate metal, and closing said dies to exert abending force by said convex die member on said sheet or plate metal atthe region of said bend and to support the ends of said temporary diemembers by said concave die member to form said bend while concurrentlyconformably bending each said temporary die member by bending stressesimparted thereto through said sheet or plate metal.

6. The method of forming corner bends in, and transverse to thecorrugations of, corrugated sheet or plate metal having a melting pointin excess of 2,000 F. while maintaining substantially uniformcorrugation cross-sectional configuration and smooth corrugation wallsurfaces throughout the bend comprising: positioning the corrugatedsheet or plate metal between spaced-apart mating convex and concavecorner bending die members with the corrugations spanning said concavedie member, one of said die members having corrugation-receiving groovesof cross-section substantially corresponding to that of thecorrugations, including in cooperative relation with each corrugation onthe side of said sheet or plate opposite said grooved die member andextending over the span of said concave die member a temporarydeformable low-carbon-content steel die member dimensioned to maintaincorrugation wall spacing, and closing said die members to form said bendwhile concurrently conformably bending each said temporary die member bybending stresses imparted thereto through said sheet or plate metal.

7. The method of forming corner bends in, and transverse to thecorrugations of, corrugated stainless steel sheet or plate metal whilemaintaining substantially uniform corrugation cross-sectionalconfiguration and smooth corrugation wall surfaces throughout the bendcomprising: positioning the corrugated stainless steel sheet or platemetal between spaced-apart mating convex and concave corner bending diemembers with the corrugations spanning said concave die member, one ofthe said die members having corrugation-receiving grooves ofcross-section substantially corresponding to that of the corrugations,including in cooperative relation with each corrugation on the side ofsaid sheet or plate opposite said grooved die member and extending overthe span of said concave die member a temporary deformablelow-carbon-content steel rod dimensioned to maintain corrugation wallspacing, and closing said die members to form said bend by the use ofbending forces exerted by said convex die member on said sheet or platemetal and on each said deformable rod at said region of said bend andcounteracting forces exerted by said concave die member at regionsremote from said region of bend.

8. The method of forming corner bends in, and transverse to thecorrugations of, stainless steel sheet or plate metal provided withcorrugations of isosceles trapezoidal cross-sectional configurationwhile maintaining substantially uniform corrugation cross-sectionalconfiguration and smooth corrugation wall surfaces throughout the bendcomprising: positioning the corrugated sheet or plate metal betweenspaced-apart and mating corner bending convex and, concave dies one ofwhich includes grooves having a corss-sectional configurationcorresponding to that of said corrugations to receive said corrugationsas the bend progresses, the corrugations of said sheet or plate metalspanning said concave die, including within each corrugation on the sideof said sheet or plate opposite said grooved die and extending over thespan of said concave die an elongated linear relatively rigidlubrication-free temporary deformable die member of low-carbon-contentsteel having a circular cross-section dimensioned to maintain'corrugation wall spacing, and closing said dies to exert by said convexdie a bending force on said sheet or plate metal and said deformable diemembers at the region of said bend and counteracting forces by saidconcave die on said sheet or plate metal and said temporary die membersat regions removed from said region of said bend to form said bend whileconcurrently conformably bending each said temporary die member bybending stresses imparted thereto through said sheet or plate metal.

9. A corrugated sheet or plate metal corner bending machine comprising,a pair of mating convex and concave corner bending dies supported forrelative movement between open position receiving said sheet or platemetal therebetween with the corrugations spanning said concave die inthe direction of their length and closed position at which a desiredcorner bend is formed, one of said dies having corrugation-receivinggrooves of cross-section substantially corresponding to that of thecorrugations of said sheet or plate metal, a temporary deformable metaldie member individual to and positionable within and extendingsubstantially throughout the ultimate die-engaged length of eachcorrugation included in a corner bend, each said temporary die memberbeing dimensioned with relation to the corrugation wall spacing tomaintain said wall spacing during corner bending thereof, and means forefiecting forced movement of said corner bending dies to said closedposition concurrently to bend said sheet or plate metal and each saidtemporary die member.

10. A corrugated sheet or plate metal corner bending machine comprising,a pair of mating convex and concave corner bending dies supported forrelative movement between open position receiving said sheet or platemetal therebetween with the corrugations spanning said concave die inthe direction of their length and closed position at which a desiredcorner bend is formed, the corrugations of said sheet or plate metalhaving isosceles trapezoidal cross-section, one of said dies havingcorrugationreceiving grooves of cross-section substantiallycorresponding to that of the corrugations of said sheet or plate metal,a temporary deformable metal die member of circular cross-sectionindividual to and positionable within and extending substantiallythroughout the ultimate dieengaged length of each corrugation includedin a corner bend, each said temporary die member being dimensioned withrelation to the corrugation wall spacing to maintain said wall spacingduring corner bending thereof, and means for efiecting forced movementof said corner bending dies to said closed position concurrently to bendsaid sheet or plate metal and each said temporary die member.

11. A corrugated stainless steel sheet or plate metal corner bendingmachine comprising, a pair of mating convex and concave corner bendingdies supported for relative movement between open position receivingsaid sheet or plate metal therebetween with the corrugations spanningsaid concave die in the direction of their length, and closed positionat which a desired corner bend is formed, the corrugations of said sheetor plate metal having isosceles trapezoidal cross-section and one ofsaid dies having corrugation-receiving grooves of crosssectionaldimensions and configuration substantially corresponding to that of thecorrugations of said sheet or plate metal, an elongated linear temporarydeformable die member of low-carbon-content steel rod individual to andpositionable within and extending substantially throughout the ultimatedie-engaged length of each corrugation included in a corner bend, eachsaid temporary die member being dimensioned with relation to thecorrugation wall spacing to maintain said wall spacing during cornerbending thereof, and means for eifecting forced movement of said cornerbending dies to said closed position concurrently to bend said sheet orplate metal and each said temporary die member.

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